A liquid crystal display has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. A liquid crystal display usually needs a flexible printed circuit board to connect a variety of electronic circuits together.
Referring to FIG. 9, a conventional flexible printed circuit 900 is shown. The flexible printed circuit 900 includes a flexible substrate 910 including an upper surface 911 and a lower surface 912, a first metallic wire layer 920, a second metallic wire layer 930 and an insulating layer 940. The first metallic wire layer 920 is disposed on the upper surface 911 of the flexible substrate 910. The second metallic wire layer 930 is disposed on the lower surface 912 of the flexible substrate 910. The insulating layer 940 is disposed on the first metallic wire layer 920.
Referring also to FIG. 10, the first metallic wire layer 920 includes a plurality of first conductive metallic wires 921 substantially parallel to each other. The first conductive metallic wires 921 extend from one edge of the flexible substrate 910 to an opposite edge of the flexible substrate 910, and are covered by the insulation layer 940. Each first conductive metallic wire 921 is completely separate from the others. And two ends of each first conductive metallic wire 921 are exposed for disposing soldering materials such as tin or tin-gold alloy thereon, so as to form a first gold finger 922 and a second gold finger 923, respectively.
Referring also to FIG. 11, the second conductive metallic wire layer 930 includes a plurality of second conductive metallic wires (not labeled) substantially parallel to each other. The second conductive metallic wires are completely separate from the others. The second conductive metallic wires locate on an edge of the flexible substrate 910. The second conductive metallic wires are exposed for disposing soldering materials such as tin or tin-gold alloy thereon, so as to form a plurality of third gold fingers 935. Each of the third gold fingers 935 is opposite to a respective gold finger 922 of the first conductive metallic wire 921.
Referring to FIG. 12, at a portion of each first gold finger 922 and corresponding third gold finger 935, a soldering hole 999 is defined through the first gold finger 922, the flexible substrate 910 and the third gold finger 935. A metal layer is disposed on an inner surface of the soldering hole 999 to electrically connect the first gold finger 922 and the third gold fingers 935. The first gold fingers 922 are usually soldered to a first print circuit board (not shown) via a manual soldering process. In detail, the first gold fingers 922 contact the first printed circuit board, and a soldering iron (not shown) contacts the third gold fingers 935. The soldering materials of the first gold fingers 922 and the third gold fingers 935 are melted via heat provided by the solder iron. Then the first gold fingers 922 are soldered to the first printed circuit board along with the solidification of the soldering materials. Superfluous soldering materials flux and fill in the soldering hole 999, making the soldering more reliable. Usually, the second gold fingers 923 are electrically connected with a second printed circuit board (not shown) through an anisotropic conductive film. Thereby, electrical signals from the first printed circuit board can be applied to the second printed circuit board via the first conductive metallic wires 921.
However, in the manual soldering process or a following assembly process, a part of the first conductive metallic wires 921 connecting the first gold fingers 922 are prone to be broken off. Thus an electrical connection of the flexible printed circuit 900 is prone to be damaged, and the flexible printed circuit 900 has a low reliability.
What is needed, therefore, is a flexible printed circuit that can overcome the above-described deficiencies.